Narrative:

While on the approach we were told we were in trail of a B747. Doing 250 KTS; the approach controller said; 'air carrier X; 210 KTS.....disregard....' immediately a supervisor got on the frequency and issued a 210 KT restr to us. I pulled the thrust levers to idle to slow and asked captain for flaps/slats 1. We stabilized at 210 KTS. Almost immediately the aircraft started lightly jumping up and down. Captain and I both mentioned immediately that we thought maybe we were getting caught in the 747's wake. The aircraft yoke then went to a full right deflection (autopilot was on). This triggered a caution so I disconnected the autopilot and took control. I tried to stabilize the roll rate and captain helped me with the rudder inputs. I put the engines into climb thrust because I feared that the severe wake turbulence would induce a stall. Captain shouted for me to roll left or right to get out of it. Because I had full right aileron; I elected to roll left. The aircraft then stabilized and captain got on the radio and told dfw ATC about our altitude deviation due to the encounter. ATC never said a word other than that they started giving us different vectors. We encountered severe wake turbulence which made the aircraft nearly uncontrollable. We did not have a visual of the 747. Dfw air traffic control failed to give us proper separation behind the 747. Dfw ATC needs to do a better job of separating heavy aircraft from smaller ones. This event could have been much worse than it turned out to be.

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Original NASA ASRS Text

Title: AN IMC CRJ700 ENCOUNTERED SEVERE WAKE TURB BEHIND A B747 ON APCH TO DFW BECAUSE OF IMPROPER SEPARATION BY ATC.

Narrative: WHILE ON THE APCH WE WERE TOLD WE WERE IN TRAIL OF A B747. DOING 250 KTS; THE APCH CTLR SAID; 'ACR X; 210 KTS.....DISREGARD....' IMMEDIATELY A SUPERVISOR GOT ON THE FREQUENCY AND ISSUED A 210 KT RESTR TO US. I PULLED THE THRUST LEVERS TO IDLE TO SLOW AND ASKED CAPT FOR FLAPS/SLATS 1. WE STABILIZED AT 210 KTS. ALMOST IMMEDIATELY THE ACFT STARTED LIGHTLY JUMPING UP AND DOWN. CAPT AND I BOTH MENTIONED IMMEDIATELY THAT WE THOUGHT MAYBE WE WERE GETTING CAUGHT IN THE 747'S WAKE. THE ACFT YOKE THEN WENT TO A FULL R DEFLECTION (AUTOPILOT WAS ON). THIS TRIGGERED A CAUTION SO I DISCONNECTED THE AUTOPILOT AND TOOK CONTROL. I TRIED TO STABILIZE THE ROLL RATE AND CAPT HELPED ME WITH THE RUDDER INPUTS. I PUT THE ENGINES INTO CLB THRUST BECAUSE I FEARED THAT THE SEVERE WAKE TURBULENCE WOULD INDUCE A STALL. CAPT SHOUTED FOR ME TO ROLL L OR R TO GET OUT OF IT. BECAUSE I HAD FULL R AILERON; I ELECTED TO ROLL L. THE ACFT THEN STABILIZED AND CAPT GOT ON THE RADIO AND TOLD DFW ATC ABOUT OUR ALTITUDE DEVIATION DUE TO THE ENCOUNTER. ATC NEVER SAID A WORD OTHER THAN THAT THEY STARTED GIVING US DIFFERENT VECTORS. WE ENCOUNTERED SEVERE WAKE TURBULENCE WHICH MADE THE ACFT NEARLY UNCONTROLLABLE. WE DID NOT HAVE A VISUAL OF THE 747. DFW AIR TRAFFIC CONTROL FAILED TO GIVE US PROPER SEPARATION BEHIND THE 747. DFW ATC NEEDS TO DO A BETTER JOB OF SEPARATING HEAVY ACFT FROM SMALLER ONES. THIS EVENT COULD HAVE BEEN MUCH WORSE THAN IT TURNED OUT TO BE.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.